For a number of years, flexible ducting for heating and air conditioning systems has been manufactured by helically laminating a polymer strip material with a wire reinforcement to form a tube. The wire reinforcement ensures roundness integrity, and the tube is substantially non-insulating. Thermal insulation is provided by a soft blanket made from fibreglass or polymer based fiber, wrapped about the tube and secured with an outer sheath of polymer film or aluminium tube material. The insulation blanket and the securing outer sheath are generally applied manually as a secondary manufacturing process, with the aid of appropriate jigs and fixtures.
This style of ducting is still predominant. However, with the increasing load of air conditioning systems on electricity supply grids, and a general desire for more thermally efficient systems, there has been a need to develop ducting with improved thermal protection.
To address this need, Australian patent 773565 discloses a flexible tubular duct that comprises a strip of flexible substrate material with a rounded portion that encapsulates a solid core of insulating material and is helically wound to form the tubular duct. The core is cylindrical in shape and is a sliver or continuous length of insulation material. The tubular duct also includes a helically wound reinforcement element which is encapsulated by the strip of substrate material in the tubular duct.
The duct construction of patent 773565 exhibits good thermal insulation properties, and is efficiently formed with its insulation in a single automatic manufacturing operation.
It is an object of the invention to provide one or more improvements in the manufacture of flexible tubular duct such as duct of the kind disclosed in patent 773565.
It is a further object of the invention to provide an improved flexible tubular duct.